This invention relates to control linkages and, more specifically, to control linkages for transmissions such as torque converter transmissions used in lift trucks or the like.
There are a variety of potential uses for control linkages of the indexing type wherein an element to be controlled must be moved, bi-directionally and serially, through a plurality of positions, one at a time, and wherein the manual actuator is restored to a particular position after each actuation, regardless of the one of many possible states of the mechanism to be controlled. A typical example is a torque converter transmission for a lift truck. Frequently, the transmission will be capable of plural forward speeds as well as plural reverse speeds and it is desirable that a change from one speed range to the other in the same direction, or the opposite direction, be accomplished in a stepwise fashion without the skipping of a speed range to minimize the number of actuators employed. In many cases, both a clutch actuator and a transmission actuator might be employed, requiring independent movement of two actuators by the operator.
In any event, many such systems in use today are extremely complex, either mechanically or electrically, or both, and a goodly number are not foolproof in terms of preventing an operator from skipping a speed range entirely.
There are, of course, a number of other uses which will occur to those skilled in the art, other than transmission control, wherein the control of mechanisms confronts the same problems.